1. Field of the Invention
The present invention relates to a technology for removing background from an image.
2. Description of the Related Art
Recent progress in networking of copiers allows a user to use functions of a copier from another terminal connected to the copier via a network. For example, it has been proposed, and increasingly used, to deliver image data input to a digital color multifunction product (e.g., image data read by a scanner) to another terminal such as a computer connected to the digital color multifunction product via a network.
In the case of delivery of scanned image data, various processing conditions are set from the digital color multifunction product or the terminal at a delivery destination. According to the processing conditions, image data is read by a scanner, subjected to predetermined processing such as conversion, and sent to the delivery destination.
Japanese Patent Application Laid-Open No. 2000-333026 discloses a conventional technology concerning image scanning, image processing, etc. performed to deliver scanned image data. In the conventional technology, a system includes an image forming unit, such as a copier, with an expansion box based on the architecture of a general-purpose computer system as a server to enhance the functions. Scanned images are stored in a hard disk in the expansion box, and image files stored therein are shared by computer systems connected to a network, which can be realized by their server functions.
Besides, upon using a scan box function (one of the functions of delivering a scanned image to a client computer), a scanned image is processed in such a manner as follows. An original image is scanned and processed according to processing conditions set by input operation. Because the scan box function is used when an image is not to be necessarily printed out, a yellow, magenta, cyan and black (YMCK) data format for printout is not created. In other words, color coordinate conversion of a scanned image from red, green, blue (RGB) to YMCK, gradation correction, compression of image data, etc. are not performed, and RGB data is stored in a scan box. A client computer on a network obtains the RGB data from the scan box, and transfers the RGB data to a local disk or the like, i.e., a storage of the client computer. The client computer displays the scanned image on a monitor screen based on the RGB data.
As described above, in the conventional technology, it is not that RGB data of a scanned image is directly stored in a hard disk and the image format of stored data is converted to deliver the stored data on the basis that image data in RGB data format is used in a computer terminal at a delivery destination. Therefore, for clients that request delivery of stored data under different image format conditions, the format of the data may not be converted to meet the requests. In the case of an image processing apparatus having a delivery function with an image forming unit such as a copier, there is an advantage that productivity of image formation can be improved by storing an input image in a dedicated data format convenient for image formation. With the RGB data format as in the conventional technology, this advantage cannot be used.
For this reason, there is recently a demand for a function of converting RGB image data stored in a scan box into CMYK data and, then, delivering the CMYK data to an apparatus with an image forming unit such as a copier.
Japanese Patent Nos. 2602681 and 2627753 disclose a color image processing apparatus and a color image processing method for converting RGB data into CMYK data.
Incidentally, the digital color multifunction product and the like perform background removal for correcting the density of the background color of an image for read RGB signals. There are various algorithms for detecting the background color of an image to correct the density. However, with all the algorithms, the correction is performed assuming that a detected background color is white. Thus, the balance of RGB varies according to whether background removal process is ON or OFF, which leads to the problem of color changes. In particular, this poses a significant problem in a color mode in which faithful reproduction of highlight color tint is required.